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Anatomy and Physiology II > Lesson 15-17 - Digestive System > Flashcards

Lesson 15-17 - Digestive System Flashcards

1
Q

digestive system

A

organ system that processes food, extracts nutrients, and eliminates residue

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2
Q

five stages of digestion

A
  1. ingestion
  2. digestion
  3. absorption
  4. compaction
  5. defecation
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3
Q

five stages of digestion: ingestion

A

selective intake of food

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4
Q

five stages of digestion: digestion

A

mechanical and chemical breakdown of food into a form usable by the body

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5
Q

five stages of digestion: absorption

A

uptake of nutrient molecules into the epithelial cells of the digestive tract and then into blood and lymph

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6
Q

five stages of digestion: compaction

A

absorbing water and consolidating the indigestible residue into feces

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7
Q

five stages of digestion: defecation

A

elimination of feces

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8
Q

mechanical digestion

A

the physical breakdown of food into smaller particles

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9
Q

three processes of mechanical digestion

A
  • cutting and grinding action of the teeth
  • churning action of the stomach and small intestines
  • the above exposes more food surface to digestive enzymes
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10
Q

chemical digestion

A

a series of hydrolysis reactions that breaks dietary macromolecules into their monomers

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11
Q

how is chemical digestion carried out?

A

by digestive enzymes produced by salivary glands, stomach, pancreas, and the small intestine

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12
Q

digestive enzymes break down polysaccharides into…

A

monosaccharides

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13
Q

digestive enzymes break down proteins into…

A

amino acids

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14
Q

digestive enzymes break down fats into…

A

monoglycerides and fatty acids

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15
Q

digestive enzymes break down nucleic acids into…

A

nucleotides

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16
Q

what happens to nutrients that are already in usable forms?

A

the are directly absorbed without being digested

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17
Q

nutrients that can be directly absorbed (5)

A
  • vitamins
  • amino acids
  • minerals
  • cholesterol
  • water
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18
Q

the digestive system has two subdivisions

A
  • digestive (alimentary) tract
  • accessory organs
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19
Q

the digestive tract includes these structures (6)

A

mouth, pharynx, esophagus, stomach, small intestine, large intestine

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20
Q

the gastrointestinal tract refers to…(2)

A

the stomach and intestines

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21
Q

accessory organs of the digestive system include (6)

A

teeth, tongue, salivary glands, liver, gallbladder, and pancreas

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22
Q

four layers of the digestive tract

A
  1. mucosa
  2. submucosa
  3. muscularis externa
  4. serosa
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23
Q

four layers of the digestive tract: mucosa (3)

A

the innermost layer comprised of epithelium, lamina propria, and muscularis mucosae

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24
Q

four layers of the digestive tract: muscularis externa (2)

A

an inner circular layer and outer longitudinal layer of smooth muscle

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25
Q

the epithelial layer of the digestive mucosa consists mostly of what cell type?

A

simple columnar

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26
Q

in the epithelial layer of the mouth through the esophagus and in the lower anal canal, what cell type is there?

A

stratified squamous

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27
Q

lamina propria of the digestive tract

A

a loose connective tissue layer found between the epithelium and muscularis mucosae

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28
Q

muscularis mucosae

A

a thin layer of smooth muscle that tenses the mucosa, creating grooves and ridges that enhance surface area contact with food

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29
Q

what is the purpose of the muscularis mucosae?

A

it improves the efficiency of digestion and nutrient absorption

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30
Q

mucosa-associated lymphatic tissue (MALT)

A

lymphocytes and lymph nodules of the digestive tract

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31
Q

submucosa

A

thick layer of loose connective tissue

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32
Q

the MALT extends into the _____ in some parts of the GI tract

A

submucosae

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33
Q

the submucosa contains…(3)

A
  • blood vessels
  • lymphatic vessels
  • a nerve plexus
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34
Q

in some places of the submucosa, there are _____-_____ glands that dump lubricating _____ into the lumen

A

mucus-secreting, mucus

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35
Q

in some places, which layer of the muscularis externa thickens to form valves (sphincters)? what do they do?

A

inner circular smooth muscles; regulate the passage of material through the tract

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36
Q

what is responsible for the motility that propels food and residue through the digestive tract?

A

the muscularis externa

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37
Q

the serosa is composed of…(2)

A

a thin layer of areolar tissue topped by simple squamous mesothelium

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38
Q

where does the serosa being? where does it end?

A

beings 3-4cm of the esophagus and ends just before the rectum

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39
Q

some organs have no serosa but are surrounded by the _____

A

adventitia

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40
Q

adventitia

A

fibrous connective tissue layer that binds and blends adjacent organs

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41
Q

where can you find the adventitia? (3)

A

the pharynx, most of the esophagus, and the rectum

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42
Q

enteric plexus

A

nervous network that regulated digestive tract motility, secretion, and blood flow

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43
Q

where is the enteric plexus? (3)

A
  • esophagus
  • stomach
  • intestines
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44
Q

the enteric plexus can/cannot function independently of the CNS

A

can; but the CNS usually exerts influence on its action

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45
Q

the enteric plexus is composed of two neuronal networks

A
  1. submucosal plexus
  2. myenteric plexus
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46
Q

submucosal plexus (2)

A

controls glandular secretions of the mucosa, and movements of the muscularis mucosae

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47
Q

where is the submucosal plexus found?

A

submucosa

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48
Q

myenteric plexus

A

ganglia and nerve fibers that control peristalsis and other contractions of the muscularis externa

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49
Q

where is the myenteric plexus found?

A

between the two layers of the muscularis externa

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50
Q

the enteric plexus includes sensory neurons that monitor…

A

tension in the gut wall and conditions in the lumen

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51
Q

the enteric plexus is often considered part of what section of the nervous system?

A

autonomic nervous system

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52
Q

mesentery

A

connective tissue sheet that suspends the stomach and intestines from the abdominal wall

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53
Q

the looseness of the mesentery allows for…

A

the stomach and intestines to undergo strenuous contractions with freedom of movement in the abdominal cavity

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54
Q

the mesentery prevents the intestines from…

A

becoming twisted and tangled by changes in body position and by its own contractions

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55
Q

the mesentery holds…

A

the viscera in proper relationship to each other

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56
Q

the mesentery provides a passage for…

A

blood vessels and nerves that supply the digestive tract

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57
Q

the mesentery contains many….(2)

A

lymph nodes and lymphatic vessels

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58
Q

depending on their relationship to the mesentery, digestive organs are…(3)

A

intraperitoneal or retroperitoneal

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59
Q

intraperitoneal

A

when and organ is enclosed by mesentery (serosa) on all sides

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60
Q

portions of the digestive tract that are intraperitoneal (8)

A
  • stomach
  • liver
  • jejunum
  • ileum
  • appendix
  • cecum
  • transverse colon
  • sigmoid colon
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61
Q

retroperitoneal

A

when an organ lies against the posterior body wall and is covered by peritoneum on its anterior side only

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62
Q

retroperitoneal organs are considered to be…

A

outside the peritoneal cavity

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63
Q

retroperitoneal organs of the digestive tract (5)

A
  • duodenum
  • pancreas
  • ascending colon
  • descending colon
  • rectum
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64
Q

motility and secretion of the digestive tract are controlled by….(3)

A

neural, hormonal, and paracrine mechanisms

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65
Q

neural controls over the digestive tract (2)

A
  • short (myenteric) reflexes
  • long (vagovagal) reflexes
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66
Q

short (myenteric) reflexes (2)

A
  • stretch or chemical stimulation acts through the myenteric
  • stimulated peristaltic contractions of swallowingl
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67
Q

long (vagovagal) reflexes

A
  • parasympathetic stimulation of digestive motility and secretion
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68
Q

examples of hormones that stimulate the digestive tract (2)

A

gastrin and secretin

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69
Q

hormones secreted into the blood stimulate _____ parts of the digestive tract

A

distant

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70
Q

paracrine secretions stimulate _____ target cells

A

nearby

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71
Q

the mouth is also known by these two other names

A
  • oral cavity
  • buccal cavity
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72
Q

functions of the mouth (7)

A
  • ingestion
  • taste/other sensory responses to food
  • chewing/chemical digestion
  • swallowing
  • speech
  • respiration
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73
Q

functions of the cheeks and lips of the mouth (3)

A
  • retain food and push it between teeth
  • involved in speech
  • essential for sucking and blowing actions (including suckling for infants)
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74
Q

tongue

A

muscular, bulky, but agile and sensitive organ

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75
Q

functions of the tongue (2)

A
  • manipulates food between teeth
  • senses taste and texture of food
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76
Q

lingual papillae of the tongue

A

bumps and projections that are the sites of most taste buds

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77
Q

body of the tongue

A

anterior two-thirds of the tongue

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78
Q

what portion of the tongue occupies the oral cavity?

A

the body

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79
Q

root of the tongue

A

posterior third of the tongue

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80
Q

what portion of the tongue occupies the oropharynx?

A

the root

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81
Q

vallate papillae

A

a V-shaped row of papillae that mark the boundary between the body and root of the tongue

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82
Q

intrinsic muscles of the tongue

A

produce subtle tongue movements of speech

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83
Q

where are intrinsic muscles of the tongue found?

A

contained entirely within the tongue

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84
Q

extrinsic muscles of the tongue

A

produce stronger movements of food manipulation

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85
Q

lingual glands (2)

A

serous and mucous glands within the tongue; secrete a portion of the saliva

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86
Q

where are extrinsic muscles of the tongue found?

A

with attachments outside the tongue

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87
Q

where are lingual glands of the tongue found?

A

amid the extrinsic muscles

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88
Q

lingual tonsils of the tongue are located…

A

contained in the root

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89
Q

palate

A

separates the oral cavity from the nasal cavity

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90
Q

what makes it possible to breathe while chewing food?

A

the palate

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91
Q

hard (bony) palate

A

anterior portion that is supported by the palatine processes of the maxillae and the palatine bones

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92
Q

the hard palate has….

A

palatine rugae

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93
Q

palatine rugae

A

transverse ridges that help the tongue hold and manipulate food

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94
Q

soft palate

A

posterior to the hard palate with more spongy texture

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95
Q

uvula

A

concial medial projection visible at the rear of the mouth

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96
Q

function of the uvula

A

helps retain food in the mouth until one is ready to swallow

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97
Q

the 32 adult teeth are referred to as…

A

dentition

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98
Q

functions of the dentition (3)

A
  • break down food into smaller pieces
  • make food easier to swallow
  • expose more surface area for enzymes (speeding chemicial digestion)
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99
Q

mastication

A

chewing

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100
Q

what is the first step in mechanical digestion?

A

mastication

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101
Q

function of mastication (2)

A

breaks food into smaller pieces to be swallowed and expose more surface area to digestive enzymes

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102
Q

food within the mouth stimulates…

A

oral receptors that trigger an involuntary chewing reflex

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103
Q

what muscles elevate the lower teeth to crush food? (2)

A
  • masseter
  • temporalis
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104
Q

functions of saliva (6)

A
  1. moistens mouth
  2. begins starch and fat digestion
  3. cleanses teeth
  4. inhibits bacterial growth
  5. dissolves molecules so they can stimulate taste buds
  6. mositens foods and binds it together into a soft mass (bolus) to aid in swallowing
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105
Q

saliva contains the following solutes (6)

A
  • mucus
  • electrolytes
  • lysozyme
  • IgA
  • salivary amylase
  • lingual lipase
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106
Q

electrolytes found in saliva (5)

A
  • Na+
  • K+
  • Cl-
  • phosphate
  • bicarbonate
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107
Q

what enzyme begins starch digestion in the mouth?

A

salivary amylase

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108
Q

what enzyme begins fat digestion in the mouth? (but mainly after the food is swallowed)

A

lingual lipase

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109
Q

two kinds of salivary glands

A
  • intrinsic (minor) salivary glands
  • extrinsic (major) salivary glands
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110
Q

intrinsic (minro) salivary glands

A

small glands dispersed amid other oral tissues that secrete saliva at a constant rate

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111
Q

extrinsic (major) salivary glands

A

three pairs of larger, more discrete organs connected to the oral cavity but ducts

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112
Q

the extrinsic salivary glands include…(3)

A
  • parotid glands
  • submandibular glands
  • sublingual glands
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113
Q

where are the parotid glands located?

A

located beneath the skin anterior to the earlobe

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114
Q

where are the submandibular glands located?

A

located halfway along the body of the mandible

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115
Q

where are the sublingual glands located?

A

located in the floor of the mouth

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116
Q

the sublingual gland has multiple…

A

ducts that empty posterior to the papilla of the submandibular duct

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117
Q

about how much saliva do extrinsic salivary glands secrete in one day?

A

1-1.5L

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118
Q

the salivary nuclei in the _____ _____ and _____ respond to signals generated by the presence of food

A

medulla oblongata, pons

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119
Q

the salivary nuclei are excited by…(3)

A

tactile, pressure, and taste receptors

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120
Q

these three things can stimulate salivation

A

odor, site, or thought of food

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121
Q

how does the salivary nuclei send signals to glands?

A

by way of the autonomic fibers in the facial and glossopharyngeal nerves

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122
Q

parasympathetic fibers stimulate salivary glands to produce…

A

an abundance of thin, enzyme rich saliva

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123
Q

sympathetic fibers stimulate salivary glands to produce…

A

less, and thicker, saliva with more mucus

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124
Q

pharynx

A

muscular funnel connecting the oral cavity to the esophagus and the nasal cavity to the larynx

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125
Q

where do the digestive and respiratory tracts intersect?

A

the pharynx

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126
Q

the pharynx has a deep layer of…

A

longitudinal skeletal muscle

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127
Q

the pharynx has a superficial layer of circular skeletal muscles that form?

A

pharyngeal constrictors (superior, middle, and inferior)

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128
Q

what do the pharyngeal constrictors do?

A

force food downward during swallowing

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129
Q

upper esophageal sphincter

A

the inferior pharyngeal constrictor that excludes air from the esophagus

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130
Q

esophagus

A

straight muscular tube between the pharynx and the stomach

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131
Q

the esophagus extends from…

A

the pharynx to the cardiac orifice of the stomach before passing through the esophageal hiatus in the diaphragm

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132
Q

the lower esophageal sphincter is located..

A

at the inferior end of the esophagus

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133
Q

function of the lower esophageal sphincter (2)

A
  • prevents stomach contents from regurgitating into the esophagus
  • protects esophageal mucosa from erosive stomach acid
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134
Q

heartburn

A

burning sensation produced by acid reflux into the esophagus

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135
Q

deglutition

A

swallowing

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136
Q

deglutition is…

A

a complex action involving over 22 muscles in the mouth, pharynx, and esophagus

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137
Q

deglutition is coordinated by the…

A

swallowing center

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138
Q

swallowing center

A

a pair of nuclei in the medulla oblongata

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139
Q

the swallowing center communicated with…

A

muscles of the pharynx and esophagus

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140
Q

swallowing occurs in three phases

A
  1. oral phase
  2. pharyngeal phase
  3. esophageal phase
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141
Q

swallowing: oral phase

A

the tongue forms a food bolus and pushes it into the laryngopharynx

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142
Q

where in the mouth does the food bolus accumulate?

A

in the oropharynx in front of the epiglottis

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143
Q

during the oral phase of swallowing, what happens with the epiglottis?

A

it tips posteriorly and the food bolus slides around it and into the laryngopharynx

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144
Q

swallowing: pharyngeal phase

A

the palate, tongue, vocal cords, and epiglottis block the oral and nasal cavities and airway while the pharyngeal constrictors push the colus into the esophagus

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145
Q

swallowing: esophageal phase

A

peristalsis drives the bolus downward and relaxation of the lower esophageal sphincter admits it into the stomach

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146
Q

how does peristalsis move the food bolus down the esophagus?

A

circular muscles constricts above the bolus and relaxes below it

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147
Q

what happens to food when you swallow when upright?

A

food and liquid drops through the esophagus by gravity faster than peristalsis can keep up with it

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148
Q

explain what movements occur during the pharyngeal phase of swallowing (3)

A
  • muscle pull larynx to epiglottis and cover it
  • vocal cords adduct/close to stop breathing
  • the upper esophagus widens
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149
Q

esophageal peristalsis is controlled by…(2)

A

the swallowing center and the myenteric plexus

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150
Q

stomach

A

a muscular sac in the superior left abdominal cavity immediately inferior to the diaphragm

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151
Q

what is the primary function of the stomach?

A

a food storage organ

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152
Q

chyme

A

acidic, soupy mixture of semi-digested food that passes on to the small intestine

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153
Q

other functions of the stomach (3)

A
  • mechanically breaks up food particles
  • liquifies the food
  • begins chemical digestion of proteins and fat
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154
Q

four portions of the stomach

A
  • cardiac part
  • fundic region (fundus)
  • body
  • pyloric part
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155
Q

stomach regions: cardiac part (2)

A
  • small area within about 3cm of the cardiac orifice
  • entry point of material from esophagus
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156
Q

stomach regions: fundic region (fundus)

A

dome superior to the esophageal attachment

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157
Q

stomach regions: body

A

makes up the greatest part distal to the cardiac orifice

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158
Q

stomach regions: pyloric part

A

narrower pouch at the inferior end

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159
Q

the pyloric part of the stomach is subdivided into… (3)

A
  • funnel-like atrium
  • narrower pyloric canal
  • terminating at the pylorus
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160
Q

pylorus

A

narrow passage to duodenum

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161
Q

pyloric sphincter

A

ring of smooth muscle around the pylorus

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162
Q

function of the pyloric sphincter

A

regulates the passage of chyme into the duodenum

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163
Q

the stomach mucosa is covered with what cell type?

A

simple columnar epithelium

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164
Q

the apical regions of the stomach mucosa cells are filled with _____

A

mucin

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165
Q

mucin

A

swells with water and becomes mucus after it has been secreted

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166
Q

when the stomach is empty, the mucosa and submucosa form longitudinal wrinkles called _____ _____

A

gastric rugae

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167
Q

the muscularis externa of the stomach has three layers

A
  • outer longitudinal layer
  • middle circular layer
  • inner oblique layer
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168
Q

mucous cells

A

secrete mucus

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169
Q

regenerative (stem) cells

A

divide rapidly and produce continual supply of new cells to replace cells that die

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170
Q

parietal cells (3)

A

secrete hydrochloric acid (HCl), intrinsic factor, and ghrelin during hunger

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171
Q

chief cells

A

secrete gastrin and pepsinogen

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172
Q

enteroendocrine cells

A

secrete hormones and paracrine messengers that regulate digestion

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173
Q

which glandular cell is most common?

A

chief cells

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174
Q

gastric pits

A

depressions in gastric mucosa, lined with the same columnar epithelium as the surface

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175
Q

gastric juice (3)

A

mainly a mixture of water, hydrochloric acid, and pepsin

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176
Q

how much gastric juice is produced per day?

A

2-3 L

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177
Q

functions of hydrochloric acid (3)

A
  • activates pepsin and lingual lipase
  • breaks up connective tissues and plant cell walls helping to liquify food and form chyme
  • contributes to innate immunity by destroying most ingested pathogens
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178
Q

pepsin

A

digests dietary protein into shorter peptides

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179
Q

pepsin is released by _____ cells as the inactive form _____

A

chief, pepsinogen

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180
Q

zymogen

A

inactive until removal of some amino acids causes it to become active

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181
Q

hydrochloric acid from _____ cells converts pepsinogen to pepsin

A

parietal

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182
Q

autocatalytic effect of pepsin

A

as some pepsin is formed, it converts more pepsinogen into more pepsin

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183
Q

where is protein digestion started? where is it finished?

A

started in the stomach and completed in the small intestine

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184
Q

what two enzymes play a minor role in digesting dietary fats?

A

gastric and lingual lipase

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185
Q

where is the digestion of fat completed?

A

the small intestine

186
Q

gastric lipase is secreted by _____ cells

187
Q

intrinsic factor

A

a glycoprotein secreted by parietal cells

188
Q

what is essential to absorption of vitamin B12 by the small intestine?

A

intrinsic factor

189
Q

how does intrinsic factor contribute to B12 absorption?

A

it bind to B12 and then intestinal cells absorb this complex by receptor mediated endocytosis

190
Q

vitamin B12 is needed to synthesize _____

A

hemoglobin

191
Q

vitamin b12 deficiency causes what kind of anemia?

A

pernicious anemia

192
Q

what is the only indispensable function of the stomach?

A

secretion of intrinsic factor

193
Q

_____ and _____ glands have a variety of cells that produce a variety of chemical messengers

A

gastric and pyloric

194
Q

gut-brain peptides include…(6)

A
  • substance P
  • vasoactive intestinal peptide (VIP)
  • secretin
  • gastric inhibitory peptide (GIP)
  • cholecystokinin
  • neuropeptide Y (NPY)
195
Q

during swallowing, food stimulates…

A

mechanoreceptors in the pharynx and they transmit signals to the medulla

196
Q

the swallowing center of the _____ _____ signals the stomach to _____

A

medulla oblongata, relax

197
Q

the vagus nerve relays messages from the medulla and activates….

A

the receptive-relaxation response in the stomach

198
Q

receptive-relaxation response

A

the stomach resists stretching briefly but relaxes it to hold more food

199
Q

the stomach will show a rhythm of peristaltic contractions controlled by…

A

enteric pacemaker cells

200
Q

where are the enteric pacemaker cells of the stomach found?

A

the longitudinal layer of muscularis externa

201
Q

describe peristalsis of the stomach (3)

A
  • a ring of constriction every 20 seconds
  • becomes stronger at the pyloric part
  • eventually very strong after 30 minutes
202
Q

what acts as a strong pump that breaks up semi digested food and prepares it for the intestine?

A

thick muscularis of the antrum

203
Q

_____ _____ come in waves that churn and break up the chyme into small particles

A

antral contractions

204
Q

why is only 3ml of chyme released into the duodenum? (2)

A
  • neutralize the stomach acid
  • digest nutrients little by little
205
Q

what happens if the duodenum is overfilled?

A

it inhibits gastric motility

206
Q

a typical meal is emptied from the stomach in…

A

in 4 hours

207
Q

vomiting

A

forceful ejection of stomach and intestinal contents from the mouth

208
Q

vomiting is usually preceded by…(2)

A

nausea and retching

209
Q

mechanical process of vomiting

A

thoracic expansion and abdominal contraction creating a pressure difference that dilates the esophagus and forces open the upper esophageal sphincter

210
Q

vomiting involves the _____ center in the _____ _____

A

emetic; medulla oblongata

211
Q

how does the emetic center function in vomiting?

A

integrates strong abdominal contractions combined with reverse peristalsis of gastric antrum and duodenum

212
Q

vomiting is induced by…(4)

A
  • overstretching of the stomach or duodenum
  • chemical irritants such as alcohol and bacterial toxins
  • visceral trauma
  • intense pain or physiological and sensory stimuli
213
Q

_____ and _____ enzymes partially digest protein and lesser amounts of starch and fat in the stomach

A

salivary, gastric

214
Q

most digestion and nearly all absorption occur after…

A

the chyme has passed into the small intestine

215
Q

the _____ does not absorb any significant amount of nutrients

216
Q

the stomach does absorb…(2)

A

aspirin and some lipid-soluble drugs

217
Q

alcohol is absorbed mainly by the…

A

small intestine

218
Q

the stomach is protected in three ways from harsh acidic and enzymatic environment

A
  1. mucous coat
  2. tight junctions
  3. epithelial cell replacement
219
Q

stomach: mucous coat

A

thick, highly alkaline mucus resists action of acid and enzymes

220
Q

stomach: tight junctions

A

between epithelial cells prevent gastric juice from seeping between them and digesting deeper tissue

221
Q

stomach: epithelial cell replacement

A
  • sloughed off into the chyme and digested with food
  • replaced rapidly by cell division in gastric pits
222
Q

cells of the stomach epithelial live only…

223
Q

breakdown of the protective layers of the stomach can result in…

A

inflammation and peptic ulcers

224
Q

gastritis

A

inflammation of the stomach

225
Q

gastritis can lead to peptic ulcers as…

A

pepsin and hydrochloric acid erodes the stomach wall

226
Q

most ulcers are caused by…

A

Helicobacter pylori

227
Q

how can Helicobacter pylori be treated? (2)

A

antibiotics and pepto-bismol

228
Q

risk factors for stomach ulcers (4)

A
  • psychological stress
  • hypersecretion of acid, pepsin sometimes involved
  • smoking
  • using of aspirin and other NSAIDs
229
Q

gastric secretion and motility is regulated by…

A

nervous and endocrine systems

230
Q

gastric activity is divided into three phases

A
  1. cephalic phase
  2. gastric phase
  3. intestinal phase
231
Q

gastric activity: cephalic phase

A

stomach being controlled by brain

232
Q

gastric activity: gastric phase

A

stomach controlling itself

233
Q

gastric activity: intestinal phase

A

stomach being controlled by small intestine

234
Q

in the cephalic phase, the stomach responds to…(4)

A

sight, smell, taste, or thought of food

235
Q

in the cephalic phase, sensory and mental inputs converge on the _____

A

hypothalamus

236
Q

in the cephalic phase, the hypothalamus relays signals to…

A

medulla oblongata

237
Q

_____ nerve fibers from the medulla stimulate the _____ nervous system of the stomach, stimulating gastric secretion

A

vagus, enteric

238
Q

40% of the stomach’s acid secretion occurs when?

A

the cephalic phase

239
Q

the gastric phase is the period in which…

A

swallowed food and semi-digested protein activate gastric activity

240
Q

two-thirds of gastric secretion and one half of acid secretion occurs in this phase

A

gastric phase

241
Q

ingested food stimulates gastric activity in two ways

A
  1. stretching the stomach
  2. increasing the pH of the stomach lumen
242
Q

ingested food stimulation: stretching the stomach (2)

A
  • activates the short reflex mediated through the myenteric plexus
  • activates long reflex mediated through the vagus nerves and the brainstem
243
Q

gastric secretion by stimulated by three chemicals

A
  1. acetylcholine
  2. histamine
  3. gastrin
244
Q

acetylcholine is secreted by….

A

parasympathetic nerve fibers of both reflexes

245
Q

histamine is a _____ secretion from _____ cells in the gastric glands

A

paracrine, enteroendocrine

246
Q

gastrin is a hormone produced by the enteroendocrine _____ cells in _____ glands

A

G, pyloric

247
Q

acetylcholine, histamine, and gastrin all stimulate _____ cells to secrete _____ and _____ _____

A

parietal, HCl, intrinsic factor

248
Q

_____ and _____ stimulate chief cells to secrete pepsinogen

A

gastrin, ACh

249
Q

in the intestinal phase, the duodenum responds…

A

responds to arriving chyme and moderates gastric activity through hormones and nervous reflexes

250
Q

stretching of the duodenum does what?

A

accentuates vagovagal reflex that stimulates the stomach

251
Q

in the intestinal phase, peptides and amino acids in chyme stimulate _____ cells of the _____ to secrete _____ _____, further stimulating the stomach

A

G, duodenum, intestinal gastrin

252
Q

in the intestinal phase, acids and fats trigger the _______ reflex

A

enterogastric

253
Q

enterogastric reflex

A

duodenum sends inhibitory signals to the stomach by way of enteric nervous system

254
Q

in the intestinal phase, the duodenum also signals the _____ to inhibit _____ _____

A

medulla; vagal nuclei

255
Q

inhibiting vagal nuclei…

A

reducing vagal stimulation of the stomach

256
Q

in the intestinal phase, the duodenum stimulates _____ neurons to _____ stomach activity

A

sympathetic; slow

257
Q

sympathetic neurons send _____ signals to the stomach

A

inhibitory

258
Q

in the intestinal phase, chyme also stimulates _____ _____ cells to release the hormones _____ and _____

A

duodenal enteroendocrine, secretin, cholecystokinin

259
Q

secretin and cholecystokinin stimulate the pancreas to release….

A

pancreatic fluid and gallbladder to release bile, but suppress gastric secretion

260
Q

as gastric secretion declines, the pyloric sphincter…

A

contacts tightly to limit chyme entering duodenum

261
Q

enteroendocrine cells also secrete _____-_____ _____ _____ (GIP)

A

glucose-dependent insulinotropic peptide (GIP)

262
Q

what does glucose-dependent insulinotropic peptide (GIP) do?

A

stimulates insulin secretion in preparation for processing nutrients about to be absorbed by small intestine

263
Q

liver

A

reddish-brown gland located immediately inferior to the diaphragm

264
Q

what is the body’s largest gland?

265
Q

what is the one function of the liver contributes to digestion?

A

the secretion of bile

266
Q

where does the gallbladder adhere?

A

a depression on the inferior surface of the liver

267
Q

hepatocytes

A

cells in the lobules of the liver

268
Q

after a meal hepatocytes absorb what from the blood? (5)

A
  • glucose
  • amino acids
  • iron
  • vitamins
  • other nutrients for metabolism and storage
269
Q

between meals, hepatocytes break down stored _____ and release ____ into the blood

A

glucogen, glucose

270
Q

hepatocytes remove and degrade… (4)

A
  • hormones
  • toxins
  • bile pigments
  • drugs
271
Q

hepatocytes secretes these into the blood (4)

A
  • albumin
  • lipoproteins
  • clotting factors
  • angiotensinogen
272
Q

the liver receives a mixture of….

A

(1) nutrient-laden venous blood from the intestines and (2) freshly oxygenated arterial blood from the celiac trunk

273
Q

after filtering through the liver, blood..

A

leaves the liver through the hepatic veins and drains into the inferior vena cava

274
Q

bile canaliculi

A

narrow channels into which the liver secretes bile which then drains into the right and left hepatic ducts

275
Q

common hepatic duct

A

formed from the convergence of the right and left hepatic ducts on the inferior side of the liver

276
Q

cystic duct

A

joins the common hepatic duct leading to the gallbladder

277
Q

bile duct

A

formed from the union of the cystic and common hepatic duct descending towards the duodenum

278
Q

near the duodenum, the bile duct joins the duct of the pancreas where it forms the _____ _____.

A

hepatopancreatic ampulla

279
Q

hepatopancreatic sphincter

A

regulates passage of bile and pancreatic juice into the duodenum from the ampulla

280
Q

between meals, the hepatopancreatic sphincter is…

A

closed and prevents the release of bile into the intestines

281
Q

when does the hepatopancreatic sphincter open?

A

when cholecystokinin (CCK) is released by enteroendocrine cells from the duodenum during a meal

282
Q

gallbadder

A

pear-shaped sac on the underside of the liver that stores and concentrates bile by absorbing H2O and electrolytes

283
Q

bile (6)

A

fluid secreted by the liver containing minerals, cholesterol, neutral fats, phospholipids, bile pigments, and bile acids

284
Q

the color of bile is _____ when secreted by the liver, but becomes intense _____ when concentrated in the gallbladder

A

yellow-green, green

285
Q

bilirubin

A

primary bile pigment

286
Q

where does the body get bilirubin?

A

hemoglobin decomposition

287
Q

bacteria in the intestine metabolize bilirubin to…

A

urobilinogen

288
Q

half of urobilinogen is converted to _____

289
Q

where is urobilinogen converted to urobilin? where does it go?

A

the kidney, excreted in urine

290
Q

the rest of urobilinogen is converted to _____ (not urobilin)

A

stercobilin

291
Q

where is urobilinogen converted to stercobilin? where does it go?

A

the intestine, brown color of feces

292
Q

how does bile enter the gallbadder?

A

by first filling the bile duct then overflowing into the gallbladder

293
Q

what happens to about 80% of bile acids?

A

they are reabsorbed in the ileum and returned to the liver where hepatocytes absorb and resecrete them

294
Q

what happens to the remaining 20% of bile acids?

A

are excreted in feces

295
Q

what is the body’s only way of eliminating excess cholesterol?

A

through bile in feces

296
Q

the liver synthesizes new bile acids from _____ to replace those lost in feces

A

cholesterol

297
Q

gallstones

A

hard masses in either the gallbladder or bile duct

298
Q

what are gallstone composed of? (3)

A
  • cholesterol
  • calcium carbonate
  • bilirubin
299
Q

how are gallstones usually removed?

A

laparoscopic surgery

300
Q

cholelithiasis

A

presence of gallstones

301
Q

cholelithiasis is most common in…

A

obese women over 40

302
Q

when can cholelithiasis occur?

A

when cholesterol becomes too concentrated, and it precipitates as crystals that grow in size

303
Q

cholelithiasis results in…(3)

A
  • jaundice
  • poor fat digestion
  • impaird absorption of fat-soluble vitamins
304
Q

pancreas

A

flattened, spongy retroperitoneal gland posterior to greater curvature of the stomach

305
Q

the pancreas is both an _____ and _____ gland

A

exocrine, endocrine

306
Q

endocrine portion of the pancreas

A

pancreatic islets secrete insulin and glucagon

307
Q

where is the endocrine portion of the pancreas concentrated?

A

the tail of the gland

308
Q

exocrine portion of the pancreas

A

99% of the organ, where it secretes pancreatic juice

309
Q

where does the pancreatic duct run?

A

lengthwise through the middle of the gland

310
Q

where does the pancreatic duct join the bile duct?

A

hepatopancreatic ampulla

311
Q

the hepatopancreatic sphincter controls release of both _____ and _____ _____ into the duodenum

A

bile, pancreatic juice

312
Q

accessory pancreatic duct

A

is a smaller duct that branches from the main pancreatic duct

313
Q

what is the function of the accessory pancreatic duct?

A

it bypasses the sphincter and allows pancreatic juice to be released into the duodenum even when bile is not

314
Q

pancreatic juice

A

an alkaline mixture of water, enzymes, zymogens, sodium bicarbonate, and other electrolytes

315
Q

what portion of the pancreas secretes the enzymes and zymogens of pancreatic juice?

316
Q

what portion of the pancreas secretes the sodium bicarbonate?

317
Q

what is the function of bicarbonate in pancreatic juice?

A

it buffers the HCl arriving from the stomach, raising the pH to 7

318
Q

pancreatic zymogens include…(3)

A
  • trypsinogen
  • chymotrypsinogen
  • procarboxypeptidase
319
Q

trypsinogen is secreted where?

A

the intestinal lumen

320
Q

trypsinogen is converted to trypsin by _____

A

enteropeptidase

321
Q

enteropeptidase is secreted by…

A

the brush border of the duodenum

322
Q

trypsin is autocatalytic meaning…

A

it converts trypsinogen into more trypsin

323
Q

what converts chymotrypsinogen and procarboxypeptidase into their active forms?

324
Q

trypsin plays a role in…

A

dietary protein digestion

325
Q

pancreatic amylase digests…

326
Q

pancreatic lipase digests…

327
Q

ribonuclease and deoxyribonuclease digest…

A

RNA and DNA respectively

328
Q

three stimuli are chiefly responsible for the release of pancreatic juice and bile

A
  1. acetylcholine
  2. cholecystokinin (CCK)
  3. secretin
329
Q

how does acetylcholine stimulate release of pancreatic juice and bile?

A

from the vagus and enteric nerves

330
Q

acetylcholine stimulates _____ to secrete enzymes during the _____ phase of gastric control even before food is swallowed

A

acini, cephalic

331
Q

after acetylcholine stimulation, enzymes released remain in _____ and _____ until chyme enters the _____

A

acini, ducts, duodenum

332
Q

how does CCK stimulate the release of pancreatic juice and bile?

A

it is secreted by the mucosa of the duodenum in response to the arrival of fats in the small intestine

333
Q

cholecystokinin stimulates…(2)

A
  • pancreatic acini to secrete enzymes
  • induces contractions of the gallbladder and relaxation of the hepatopancreatic sphincter to discharge bile and pancreatic juice into the duodenum
334
Q

how doe secretin stimulate the release of pancreatic juice and bile?

A

it is released from the duodenum in response to acidic chyme arriving from the stomach

335
Q

secretin stimulates the ducts of both ______ and _____ to secrete more sodium bicarbonate

A

liver, pancreas

336
Q

after stimulating the liver/pancreas, the release of secretin causes….

A

the pH to rise to the level required for activity of the pancreatic intestinal digestive enzyme (7)

337
Q

what is the site of nearly all chemical digestion and nutrient absorption?

A

the small intestine

338
Q

what is the longest part of the digestive tract?

A

the small intestine

339
Q

the small intestine is drained by the _____ veins, which converge to the _____ _____ vein which then joins the _______ vein and flows into the ______ ______ system to the liver with its load of nutrients

A

mesenteric, superior mesenteric, splenic, hepatic portal

340
Q

small intestine

A

a coiled tube filling most of the abdominal cavity inferior to the stomach and liver

341
Q

three regions of the small intestine

A
  • duodenum
  • jejunum
  • ileum
342
Q

where does the duodenum of the small intestine begin?

A

at the pyloric valve

343
Q

most of the duodenum is _____peritoneal

344
Q

the duodenum receives…(3)

A

stomach contents, pancreatic juice, and bile

345
Q

what is the function of the duodenum? (3)

A
  • neutralizes stomach acids
  • emulsified fats
  • inactivates pepsin (elevated pH)
346
Q

when do pancreatic enzymes take over digestion?

A

in the duodenum

347
Q

the jejunum has tall, large, closely spaces _____ _____

A

circular folds

348
Q

the wall of the jejunum is…(2)

A

relatively thick and muscular

349
Q

what gives the jejunum a red color?

A

the rich blood supply

350
Q

where in the small intestine does most digestion and nutrient absorption occur?

351
Q

where is the location of the final digestion and absorption of carbohydrates, lipids, proteins, and nucleic acids

352
Q

compared to the jejunum, the ileum is..(4)

A
  • thinner
  • less muscular
  • less vascular
  • a pale pink vs. red
353
Q

aggregated lymphoid nodules

A

prominent lymphatic nodules in clusters on the side opposite to the mesenteric attachment

354
Q

aggregated lymphoid nodules become _____ near the large intestine

355
Q

ileocecal junction

A

end of the small intestine where the ileum joins the cecum of the large intestine

356
Q

the small intestine tissues are similar to those in the _____ and _____, but is specialized for _____ _____ and _____

A

esophagus, stomach; nutrient digestion, absorption

357
Q

the lumen of the small intestine is lined with what kind of cells?

A

simple columnar epithelium

358
Q

the muscularis externa of the small intestine has…(2)

A
  • thicker inner circular layer
  • thinner outer longitudinal layer
359
Q

the jejunum and ileum are _____peritoneal

A

intra - covered with serosa

360
Q

why does the small intestine have a large internal surface area? (3)

A

three types of folds/projection
- circular folds
- villi
- mircovilli

361
Q

circular folds of the small intestine increase surface area by..

A

a factor of 2-3

362
Q

the villi of the small intestine increase surface area by…

A

a factor of 10

363
Q

microvilli of the small intestine increase surface area by…

A

a factor of 20

364
Q

circular folds

A

transverse to spiral ridges up to 1 cm high

365
Q

what are the largest folds of the intestinal wall?

A

circular folds of the small intestine

366
Q

where do circular folds occur?

A

from the duodenum to the middle of the ileum

367
Q

the circular folds are not found in what portion of the small intestine?

A

the distal half of the ileum

368
Q

by what point in the small intestine is most nutrient absorption complete?

A

by the distal portion

369
Q

what is the function of the circular folds in the small intestine? (2)

A
  • causes chyme to flow in a spiral fath causing more contact with the mucosa
  • promotes more thorough mixing and nutrient absorption
370
Q

villi are covered with two types of cells

A
  • absorptive cells (enterocytes)
  • goblet cells
371
Q

what makes the digestive mucosa look fuzzy?

372
Q

the epithelia of the digestive system is joined together by _____ _____ that prevent digestive enzymes from seeping between them

A

tight junctions

373
Q

the core of a villus is filled with…

A

areolar tissue of the lamina propria

374
Q

the core of the villus contains…

A
  • arteriole
  • blood capillaries
  • venule
  • lacteal
375
Q

lacteal

A

a lymphatic vessel that absorbs dietary fats that the blood cannot absorb

376
Q

microvilli

A

small plasma membrane extensions that form a fuzzy brush border on the apical surface of each enterocyte

377
Q

what is the purpose of microvilli?

A

increase absorptive surface area and contain brush border enzymes

378
Q

brush border enzymes

A

enzymes contained in the plasma membrane of microvilli (not released into intestinal lumen)

379
Q

what enzymes carry out some of the final stages of enzymatic digestion?

A

brush border enzymes

380
Q

contact digestion

A

chyme must contact the brush border for digestion to occur

381
Q

duodenal glands

A

neutralize stomach acid and shield the mucosa from its erosive effects

382
Q

what do the duodenal glands secrete?

A

an abundance of bicarbonate-rich mucus

383
Q

what does the mucus of the duodenal glands contain?

A

signaling molecules that influence immune cells to tolerate food antigens and beneficial bacteria

384
Q

where can a large number of lymphocytes be found within the digestive tract? what do they do?

A
  • throughout the lamina propria and submucosa
  • intercept pathogens before they can invade the bloodstream
385
Q

between the bases of villi are _____ _____

A

intestinal crypts

386
Q

intestinal crypts

A

pores that open into tubular glands on the floor of the small intestine

387
Q

how far into the intestinal wall can intestinal crypts go?

A

as far as the muscularis mucosae

388
Q

intestinal crypts secrete…

A

intestinal juice

389
Q

what does intestinal juice contain? (3)

A

water, mucus, but little enzyme

390
Q

intestinal juice is secreted in response to… (3)

A
  • acid
  • hypertonic chyme
  • distension of the intestine
391
Q

most enzymes that function in the small intestine are found…(2)

A
  • brush border
  • pancreatic juice
392
Q

contractions of the small intestine serve three functions

A
  • to mix chyme with intestinal juice
  • to churn chyme and bring it in contact with mucosa for contact digestion/nutrient absorption
  • to move residue toward the large intestine
393
Q

segmentation

A

movement in which stationary ring-like constrictions appear in several places along the intestine, then relax as new constritions form elsewhere

394
Q

what is the most common kind of intestinal contraction?

A

segmentation

395
Q

what does segmentation do?

A

kneads and churns the intestinal contents

396
Q

what sets the rhythm for segmentation?

A

enteric pacemaker cells in the muscularis externa

397
Q

when does segmentation decline and peristalsis begin?

A

when most nutrients has been absorbed and little remains but undigested residue

398
Q

peristalsis

A

rhythmic contractions that move remaining contents of the small intestine toward the colon

399
Q

migrating motor complex

A

successive, overlapping waves of contraction

400
Q

food in the stomach triggers _____ reflex

A

gastroileal

401
Q

ileal papilla aka…

A

ileocecal valve

402
Q

what does the gastroileal reflex do?

A

enhances segmentation in the ileum and relaxes the ileal papilla to release material from the small intestine to the large intestine

403
Q

are vitamins digested?

A

no, they are absorbed unchanged

404
Q

what happens if vitamins are ingested without fat-containing food?

A

they are not absorbed at all but are passed into the feces and wasted

405
Q

fat-soluble vitamins (4)

A

A, D, E, and K

406
Q

water soluble vitamins (2)

A

B complex (B12) and C

407
Q

how are water soluble vitamins absorbed?

A

simple diffusion

408
Q

parathyroid hormone is secreted in response to…

A

a drop in blood calcium levels to increase calcium absorption in duodenum

409
Q

what does parathyroid hormone stimulate?

A

the kidney to synthesize vitamin D from precursors made by epidermis and liver

410
Q

most absorbed calcium is from…

A

meat and dairy

411
Q

how does the digestive system absorb water?

A

by osmosis following the absorption of salts and organic nutrients

412
Q

diarrhea

A

occurs when the large intestine absorbs too little water

413
Q

when can diarrhea occur? (2)

A
  • feces pass through too quickly if intestine is irritated
  • feces contain high concentrations of a solute
414
Q

constipation

A

occurs when fecal movement is slow and too much water gets reabsorbed, causing feces to become hardened

415
Q

where does the large intestine begin?

A

as the cecum inferior to the ileal papilla

416
Q

where is the appendix?

A

attached to the lower end of the cecum

417
Q

appendix

A

densely populated with lymphocytes and is a significant source of immune cells

418
Q

colon

A

portion of the large intestine between the ileocecal junction and the rectum

419
Q

four parts of the colon

A
  • ascending colon
  • transverse colon
  • descending colon
  • sigmoid colon
420
Q

sigmoid colon

A

s-shaped portion leading down into the pelvic cavity

421
Q

rectum

A

portion ending at the anal canal

422
Q

the rectum has three curved and three infoldings called…

A

transverse rectal folds (rectal valves)

423
Q

anal canal

A

final 3 cm of the large intestine

424
Q

hemorrhoids

A

permanently distended veins that protrude into the anal canal or bulge outside the anus

425
Q

large _____ veins from the superficial plexus in anal columns around the orifice

A

hemorrhoidal

426
Q

why are the veins around the anus subject to hemorroids?

A

they lack valves and are subject to distension

427
Q

the muscularis externa of the colon is different, as it has these components (2)

A
  • taenia coli
  • haustra
428
Q

taenia coli

A

longitudinal fibers concentrated in three thickened, ribbon-like strips

429
Q

haustra

A

pouches in the colon caused by the muscle tone of the taeniae coli

430
Q

in the rectum and anal canal, longitudinal muscles are in a continuous sheet meaning..

A

they have no haustra

431
Q

the anus is regulated by two sphincters

A
  • internal anal sphincter
  • external anal sphincter
432
Q

internal anal sphincter

A

smooth muscle of the muscularis externa

433
Q

external anal sphincter

A

skeletal muscle of the pelvic diaphragm

434
Q

the large intestine mucosa has what cell type? except in what location?

A

simple columnar epithelium; except the lower half of the anal canal

435
Q

the lower half of the anal canal has what cell type? why?

A

non-keratinized stratified squamous epithelium; resists abrasion from the passage of feces

436
Q

in the large intestine, the intestinal crypts are _____ than in the small intestine and have _____ density of goblet cells

A

deeper, greater

437
Q

the large intestine does not have these two features of the small intestine

A

circular folds or villi

438
Q

the lamina propria and submucosa layers of the large intestine have a lot of _____ tissue

439
Q

the lymphoid tissue in the large intestine is for…

A

protection from large population of bacteria in large intestine

440
Q

gut microbiome (microbiota)

A

more than 1000 species of bacteria, yeasts, viruses, and other microbes that populate the large intestine

441
Q

bacteria in the large intestine digest (3)

A
  • cellulose
  • pectin
  • other carbohydrates which out cells lack enzymes
442
Q

the gut microbiome helps synthesize what vitamins? (2)

443
Q

flatus

A

intestinal gas that is expelled

444
Q

flatus consists of…(3)

A
  • hydrogen sulfide
  • indole
  • skatol
    produce odor
445
Q

how long does the large intestine take to reduce residue to feces?

A

36 - 48 hours

446
Q

where does residue spend the most time?

A

in the transverse colon

447
Q

what does the large intestine reabsorb? (2)

A

water and electrolytes

448
Q

the solids of feces consists of? (4)

A
  • 30% bacteria
  • 30% undigested fiber
  • 10-20% fat
  • small amounts of mucus, proteins, salts, digestive secretions, and sloughed epithelial cells
449
Q

colonic motility includes..(2)

A
  • haustral contractions
  • mass movements
450
Q

haustral contractions (2)

A
  • distention of a haustrum stimulates it to contract
  • churns and mixes residue promoting water and salt absorption
451
Q

mass movements

A

stronger contractions that occur one to three times day moving residue several centimeters

452
Q

what triggers mass movements? (2)

A

the gastrocolic and duodenocolic reflexes

453
Q

what stimulates motility of the colon?

A

filling of the stomach and duodenum

454
Q

stretching of the rectum stimulates two defecation reflexes

A
  • intrinsic defecation reflex
  • parasympathetic defecation reflex
455
Q

intrinsic defecation reflex

A

stretching signals travel through plexus to the muscularis, causing it to contract and the internal sphincter to relax

456
Q

how does the intrinsic defecation reflex work?

A

entirely within the myenteric plexus to produce relatively weak response

457
Q

the parasympathetic defecation reflex involves…

A

the spinal cord

458
Q

how does the parasympathetic defecation reflex work? (2)

A
  • stretching of the rectum sends sensory signals to the spinal cord
  • pelvic nerves return signals, intensifying peristalsis and relaxing the internal anal sphincter
459
Q

defecation only occurs if…

A

the external anal sphincter and puborectalis muscles are voluntarily relaxed

460
Q

what increases abdominal pressure and compresses the rectum?

A

abdominal contractions (valsalva maneuver)

Anatomy and Physiology II (19 decks)

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